Question: Solve for $t$ : $23 = 30 + t$
Subtract $30$ from both sides: $ \begin{eqnarray} \\ \hphantom{23 {- 30}} &\hphantom{=}& \hphantom{t} \\ 23 &=& 30 + t \\ \\ {-30} && {-30} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 23 {- 30} &=& t \\ \end{eqnarray} $ Simplify. $ t = -7$